Like much of ad tech, header bidding was built to solve a desktop challenge. But mobile is eating media.

Publishers are busy adopting header bidding across the mobile web, but the technique isn’t yet gaining acceptance within mobile apps. The problem: New bidders often have to upload their own software development kits, which allow third parties to integrate their features — which in turn slows down load times and hurts user experience.

“Lots of app owners are reluctant to add more SDKs because it will slow down the app,” said Richard Ottoy, U.K. commercial director at OpenX. “And every time you add a new SDK, it requires development resources.”

Unlike mobile web header bidding, in-app header bidding features an entirely different setup than desktop header bidding. For one, the phrase “in-app header bidding” is a misnomer because there is no browser in an app and, therefore, no header of a browser for the bidder’s code to be plugged into. But the idea of header bidding – where publishers simultaneously offer inventory to multiple exchanges before making calls to their ad servers – persists within apps, so it is still relevant to compare these integrations to their desktop cousins.

Apps theoretically present a huge opportunity for publishers since eMarketer estimates that 86 percent of the time users spend on mobile is spent in apps. But publishers have struggled to monetize their content in apps, and many of the most popular apps simply do not belong to publishers. A spokesperson for App Annie said that only two (ESPN and CNN) of the top 200 most-downloaded apps last month belonged to publishers.

An analysis by Flurry shows that just 15 percent of the time spent on apps in the U.S. was spent on “music, media and entertainment” apps, which is its closest proxy for publisher apps. Facebook alone commanded more attention, sucking up nearly 20 percent of total time that U.S. users spent on apps. Although sources believed that adoption of in-app header bidding has been minimal, they were unaware of any existing research on the topic.

For publishers committed to monetizing app content, there are a few ways to implement header bidding within apps, and each has its drawbacks and benefits. Andre Baden Semper, who heads up Purch’s sales and marketing in Europe, noted that with in-app header bidding “it is all about getting those SDKs in line.”

One way is for the vendor to plug its SDK into an app. This is sort of the equivalent of having the vendor bid on page, which allows for a more direct transfer of user data but ultimately bogs down load times and drives up labor costs whenever the bidder wants to alter the setup.

In-app header bidding can also be done through server-side products. Downsides to this are that it takes a lot of technical expertise to implement, vendors have to agree on integrating with each other’s technology and buyers have to rely on the app’s ad server to obtain user data. The plus side is that it can reduce latency. There are also products that aim to blend SDK and server-side bidding within apps.

When asked about the future of mobile-app header bidding, ad tech firms (who are likely to start selling these products if they aren’t already doing so) are typically bullish that these products will gain mass adoption — it’s in their interest to be. But publishers emphasize that integrating and monitoring SDKs is resource-intensive and not always worth it.

“The mobile ecosystem is less mature in the demand partners,” said a publishing exec requesting anonymity. “Desktop has a lot of SSPs in place. But just because of the nature of apps, there is still that notion of silos with the demand sources.”